1. Field of the Invention
The present disclosure relates to power lines for distribution of electrical power, and more particularly, to an evaluation of noise and excess current on the power lines, for the sake of identifying a location of a source of the noise or excess current.
2. Description of the Related Art
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, the approaches described in this section may not be prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Partial discharge (PD) is a phenomenon that occurs in insulation of an electrical power cable that has sustained damage, such as through aging, physical damage, or exposure to excessively high electric fields. PD may afflict cables, connectors, surge arrestors, and other high voltage devices. Faulty overhead insulators may also allow for an occurrence of noise with frequency and phase characteristics similar to PD. PD generates short pulses having durations in the nanosecond range or shorter. PD pulses tend to occur at certain phases of an AC power voltage, and tend to be roughly synchronized with the power frequency or twice the power frequency. PD is a member of a class of noise known as line-synchronized noise or line-triggered noise. PD pulses have a continuous broadband spectrum that typically includes a range between one kilohertz and hundreds of megahertz.
U.S. Pat. No. 7,532,012 describes several techniques for capturing a PD pulse, and also describes several parameters for evaluating waveforms to distinguish between waveforms relating to line-frequency-synchronized phenomena, such as PD pulses, and external interference, termed “ingress”, not having line frequency periodicity. For waveforms distinguished as deriving from PD, these parameters have the further utility of quantifying the intensity of that PD.
A deteriorating cable may also suffer from very brief high current pulses, as might be expected from an arc or other temporary short circuit that clears itself. It is desirable to identify the deteriorating cable, and more particularly, its specific location, before it fails completely.
The present document discloses several techniques for distinguishing and quantifying PD and excess current, and identifying a location of a source of the PD or excess current.